Interest in, and evidence or, the relationships between adverse perinatal and early infant risk factors, and important diseases emerging during adulthood, has led to plans by the Federal Government to conduct a cohort study called the National Children's Study (NCS) of over 100,000 births. The NCS has similarities to a study conducted during the 1960's called the Collaborative Perinatal Project (CPP), in which 58,000 live births were followed to age 7 or 8 in 12 university medical centers in the United States. The CPP included detailed data pertaining to pregnancy and birth (including maternal and cord sera, still available for study); repeated observations of the offspring's physical, neurological, cognitive, and behavioral development; social and environmental characteristics at birth and age 7; and fetal, neonatal, later infant, and child death. Pilot and developmental work is proposed in support of a health follow-up of the Baltimore cohort of the CPP (n = 4034). Between 1992 and 1994, a random sample of 2694 of the Baltimore CPP cohort of births, and their mothers, was surveyed, in the Pathways to Adulthood Study (PAS). The follow-up to be proposed at the completion of this proposed pilot study would occur when the cohort was about 45 years old. Pilot work is needed before a proposal for a more intensive and complete follow-up of the Baltimore CPP can be justified. First, we propose to assess the degree to which cohort members can be located and are willing to participate in a follow-up, by a pilot study of 160 offspring, in four groups defined by their level of participation in the Baltimore CPP and PAS projects. Second, we propose to evaluate the cost and utility of converting certain data from the Baltimore CPP hardcopy records to magnetic form. Third, we propose to compare traditional and new statistical techniques for understanding the consequences of specific fetal growth trajectories, with data on more than 1700 respondents, already in hand, relevant to two particular outcomes in young adults: mental health and obesity. Success in this pilot and developmental work will be followed by a proposal for health follow-up of a large and carefully designated sample of the Baltimore CPP, or possibly the entire Baltimore CPP cohort. The health follow-up will entail a household interview and medical examination. In the planned follow-up, we will obtain blood for DNA and other biomarkers. The follow-up will begin study in this cohort of the chain of causes linking early environmental risk, fetal, and infant development to disorders of young adulthood, such as mental conditions, through to diseases which have onset in middle age, such as diabetes, hypertension, heart disease, and stroke. The future project will also establish sub-samples at risk for new onset of these diseases in the coming decade of life. The Baltimore CPP cohort has been more intensively studied than any other CPP cohort. Data from the proposed study will anticipate those of the NCS by nearly half a century. The results will generate new information about early influences on a large range of prevalent, disabling and fatal health conditions.